The present invention relates to the structure of a solid state image sensor and a system using the solid state image sensor.
Conventional video input systems using solid state image sensors have been used for video cameras which record motion video data on tapes, supervisory cameras, still video cameras which record still video data on video floppy disks and digital memory media, industrial cameras, and the like. Most of these systems use area CCD image sensors.
An area CCD image sensor includes a photoelectric converter constituted by a two-dimensional array of photoelectric elements corresponding to pixels. An optical image is formed on this photoelectric converter. Signals converted into charges by the photoelectric converter are sequentially read out as pixel signals by a vertical transfer CCD and a horizontal transfer CCD.
As another solid state image sensor, a MOS type image sensor is available. The MOS type image sensor uses no CCDs for vertical and horizontal transfer. In this sensor, pixels selected by selection lines constituted by aluminum lines are read out through read. lines, like a memory device. The MOS type image sensors were once actually used for video cameras. However, the MOS type image sensors were replaced with CCD image sensors because the MOS type image sensors cause larger noise than the CCD image sensors.
The MOS type image sensor, however, has characteristic features which the CCD image sensor does not have. For example, a CMOS type image sensor is driven by a single drive source unlike the CCD image sensor which is driven by multiple drive sources.
More specifically, to drive the CCD image sensor, a plurality of positive and negative power supply potentials, e.g., +20V, +15V, and xe2x88x9210V, are required. In contrast to this, the MOS type image sensor can be driven by a single power supply of, e.g., +5V; it requires only one power supply potential. The same power supply voltage as that used for other circuits making up an image sensing system, e.g., an amplification circuit and a control circuit, can be used for the MOS type image sensor. The number of power supplies can therefore be decreased.
The power consumption of the MOS type image sensor is also smaller than that of the CCD image sensor.
The MOS type image sensor has another characteristic feature which the CCD image sensor does not have. That is, a logic circuit, an analog circuit, an analog/digital conversion circuit, and the like can be easily formed on the sensor by using a single MOS circuit manufacturing process. It is a well-known fact that peripheral circuits, associated circuits, and the like can be easily formed on the MOS type image sensor. Prototypes of such sensors have been reported at academic meetings (e.g., ISSCC in 1996).
As described above, the MOS type image sensor has characteristic features which the CCD image sensor does not have. To make the most of these characteristic features, however, a circuit structure in the sensor which is suited to a system to be used and an interface for other circuit portions are required. If, for example, an appropriate interface is not used, a large number of pins are required to result in an increase in the chip area of the sensor or the size of the package. An increase in cost cannot therefore be avoided.
Video compression techniques for teleconferences, videophones, and the like have been standardized. With the widespread use of personal computers and communication services for personal computers, a desktop conference using personal computers will soon become a reality. Image compression techniques are also used for this purpose.
A video camera recorder or a portable video camera is used for an image capture section of such a video system. Outputs from these cameras are still analog video outputs. It is as a matter of course that in the future such cameras are connected to personal computers by digital direct coupling or incorporated therein. If a solid state image sensor incorporating a video processing circuit is available as an image sensor used for such purposes, the number of parts can be decreased. A reduction in cost can therefore be attained.
As described above, the MOS type image sensor as a solid state image sensor has many advantages over the CCD image sensor except for noise. With advances in noise suppression techniques, the MOS type image sensor has regained attention. When the MOS type image sensor is to be used as an image sensing device, a pixel selection function, an image compression function, a low speed shot control function, an image data conversion function, and the like may be implemented as MOS circuits on the same chip as that of the MOS type image sensor, in addition to an image sensing function. With this structure, only processing results can be used. As a result, a reduction in load can be attained in terms of design and manufacture of an actual system using the MOS type image sensor to take place of peripheral circuits for the above functions.
If, therefore, a solid state image sensor with video processing circuits is available as an image sensor, the number of parts can be reduced, and a reduction in cost can be attained.
If, however, these video processing circuits are simply implemented on the chip of the MOS type image sensor, a problem is posed in terms of operability when this chip is applied to a system. If, for example, a function is designed on the basis of the specifications required by the user, the resultant device becomes a single-function device. That is, a dedicated device, i.e., a device used for a special purpose, is obtained, resulting in poor versatility.
Considering the social background of an information-oriented society and the popularity of multimedia, an image capture function will be increasingly required in various fields. In addition, with increasing demand in space and energy savings, reductions in the size and power consumption of a function element are required. Under the circumstances, it is urgently necessary to realize a high-performance, high-versatility solid state image sensor using a MOS type image sensor which can meet these demands.
It is an object of the present invention to provide a compact, high-performance solid state image sensor having high general versatility and using a MOS type image sensor capable of energy-saving. It is another object of the present invention to provide a video system using this solid state image sensor.
According to the first aspect of the present invention, there is provided a solid state image sensor comprising: an area sensor section in which pixels for performing photoelectric conversion are arranged two-dimensionally; a pixel selection section for selecting a pixel of the area sensor section and reading out a pixel signal from the pixel; an analog signal processor section for performing signal processing for the pixel signal read out from the pixel; an analog-digital conversion section for converting the processed signal into a digital signal; a digital signal processor section for processing to convert the digital signal into luminance and color difference signals; and an interface section which can externally output the digital video signal, operates in accordance with an external command, and has a function of selecting one of the digital signal from the analog-digital conversion section and luminance and color difference signals, wherein the area sensor section, the pixel selection section, the analog signal processor section, the analog-digital conversion section, the digital signal processor section, and the interface section are mounted on a single chip.
According to the second aspect of the present invention, there is provided a solid state image sensor comprising: an area sensor section in which pixels for performing photoelectric conversion are arranged two-dimensionally; a pixel selection section for selecting a pixel of the area sensor section and reading out a pixel signal from the pixel; an analog signal processor section for performing signal processing for the pixel signal read out from the pixel; an analog-digital conversion section for converting the processed signal into a digital signal; a digital signal processor section for performing motion video processing and still image processing; and an interface section which can externally output the digital video signal, operates in accordance with an external command, and has a function of selecting one of a motion video signal obtained by performing the motion video processing and a still image signal obtained by performing the still image processing, wherein the area sensor section, the pixel selection section, the analog signal processor section, the analog-digital conversion section, the digital signal processor section, and the interface section are mounted on a single chip.
According to the third aspect of the present invention, there is provided a solid state image sensor comprising: an area sensor section in which pixels for performing photoelectric conversion are arranged two-dimensionally; a pixel selection section for selecting a pixel of the area sensor section and reading out a pixel signal from the pixel; an analog signal processor section for performing signal processing for the pixel signal read out from the pixel to output a processed signal; an analog-digital conversion section for converting the processed signal into a digital signal; a digital signal processor section including means for performing signal processing for the digital signal to convert the digital signal into a digital video signal having a predetermined signal format, and storage means for storing the digital video signal; and an interface circuit for externally outputting the digital video signal from the storage means in accordance with an external command, wherein the area sensor section, the pixel selection section, the analog signal processor section, the analog-digital conversion section, the digital signal processor section, and the interface section are mounted on a single chip.
According to the fourth aspect of the present invention, there is provided a solid state image sensor comprising: an area sensor section in which pixels for performing photoelectric conversion are arranged two-dimensionally; a pixel selection section for selecting a pixel of the area sensor section and reading out a pixel signal from the pixel; an analog signal processor section for performing signal processing for the pixel signal read out from the pixel; an analog-digital conversion section for converting the processed signal into a digital signal; a digital signal processor section for performing signal processing to convert the digital signal into a digital video signal having a predetermined signal format; an interface section for externally outputting the digital video signal and inputting an external command; and means capable of changing a charge integration time for at least some of the pixels in accordance with an external command, wherein the area sensor section, the pixel selection section, the analog signal processor section, the analog-digital conversion section, the digital signal processor section, the interface section, and the means are mounted on a single chip.
According to the fifth aspect of the present invention, there is provided a solid state image sensor comprising: an area sensor section in which pixels for performing photoelectric conversion are arranged two-dimensionally; a pixel selection section for selecting a pixel of the area sensor section and reading out a pixel signal from the pixel; an analog signal processor section for performing signal processing for the pixel signal read out from the pixel; an analog-digital conversion section for converting the processed signal into a digital signal; a digital signal processor section for performing signal processing to convert the digital signal into luminance and color difference signals; and an interface section for externally outputting the digital video signal by alternately outputting the luminance and color difference signals, wherein the area sensor section, the pixel selection section, the analog signal processor section, the analog-digital conversion section, the digital signal processor section, and the interface section are mounted on a single chip.
According to the sixth aspect of the present invention, there is provided a solid state image sensor comprising: an area sensor section in which pixels for performing photoelectric conversion are arranged two-dimensionally; a pixel selection section for selecting a pixel of the area sensor section and reading out a pixel signal from the pixel; an analog signal processor section for performing signal processing for the pixel signal read out from the pixel; an analog-digital conversion section for converting the processed signal into a digital signal; a digital signal processor section for performing signal processing to convert the digital signal into a digital video signal having a predetermined signal format; an information section which holds information indicating characteristic of the sensor; and an interface section which externally outputs the digital video signal, can input an external command, and allows the information to be read out in accordance with the external command, wherein the area sensor section, the pixel selection section, the analog signal processor section, the analog-digital conversion section, the digital signal processor section, the information section and the interface section are mounted on a single chip.
According to the seventh aspect of the present invention, there is provided a video system comprising: a solid state image sensor including: an area sensor section in which pixels for performing photoelectric conversion are arranged two-dimensionally, a pixel selection section for selecting a pixel of the area sensor section and reading out a pixel signal from the pixel, a signal processor section for performing signal processing for the pixel signal read out from the pixel and outputting at least one of a digital video signal, an analog video signal, a status signal, and characteristic information of the solid state image sensor, and an interface section which operates in response to an external command and externally outputs at least one of a digital video signal, a status signal, and characteristic information of the solid state image sensor, wherein the area sensor section, the pixel selection section, the signal processor section, and the interface section are mounted on a single chip; and a visual processing unit for performing visual information processing by using at least one of a digital video signal, an analog video signal, a status signal, and characteristic information of said solid state image sensor which are output from said solid state image sensor.
Additional object and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The object and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.